On 8/23/21 10:54, Martin Liška wrote:
On 8/16/21 13:13, Martin Liška wrote:
I'm going to apply the following 3 tested patches.
Martin
One more patch I've just tested.
Martin
And one more backport.
Martin
From 64fbc25cb6983725fefe313bfedd3657df795d54 Mon Sep 17 00:00:00 2001
From: Martin Liska <mli...@suse.cz>
Date: Fri, 13 Aug 2021 17:22:35 +0200
Subject: [PATCH] Speed up jump table switch detection.
PR tree-optimization/100393
gcc/ChangeLog:
* tree-switch-conversion.c (group_cluster::dump): Use
get_comparison_count.
(jump_table_cluster::find_jump_tables): Pre-compute number of
comparisons and then decrement it. Cache also max_ratio.
(jump_table_cluster::can_be_handled): Change signature.
* tree-switch-conversion.h (get_comparison_count): New.
(cherry picked from commit c517cf2e685e2903b591d63c1034ff9726cb3822)
---
gcc/tree-switch-conversion.c | 42 ++++++++++++++++++++----------------
gcc/tree-switch-conversion.h | 14 ++++++++++--
2 files changed, 35 insertions(+), 21 deletions(-)
diff --git a/gcc/tree-switch-conversion.c b/gcc/tree-switch-conversion.c
index 7f65c4ce839..8fc5eaa3033 100644
--- a/gcc/tree-switch-conversion.c
+++ b/gcc/tree-switch-conversion.c
@@ -1090,7 +1090,7 @@ group_cluster::dump (FILE *f, bool details)
for (unsigned i = 0; i < m_cases.length (); i++)
{
simple_cluster *sc = static_cast<simple_cluster *> (m_cases[i]);
- comparison_count += sc->m_range_p ? 2 : 1;
+ comparison_count += sc->get_comparison_count ();
}
unsigned HOST_WIDE_INT range = get_range (get_low (), get_high ());
@@ -1185,11 +1185,24 @@ jump_table_cluster::find_jump_tables (vec<cluster *> &clusters)
min.quick_push (min_cluster_item (0, 0, 0));
+ unsigned HOST_WIDE_INT max_ratio
+ = (optimize_insn_for_size_p ()
+ ? param_jump_table_max_growth_ratio_for_size
+ : param_jump_table_max_growth_ratio_for_speed);
+
for (unsigned i = 1; i <= l; i++)
{
/* Set minimal # of clusters with i-th item to infinite. */
min.quick_push (min_cluster_item (INT_MAX, INT_MAX, INT_MAX));
+ /* Pre-calculate number of comparisons for the clusters. */
+ HOST_WIDE_INT comparison_count = 0;
+ for (unsigned k = 0; k <= i - 1; k++)
+ {
+ simple_cluster *sc = static_cast<simple_cluster *> (clusters[k]);
+ comparison_count += sc->get_comparison_count ();
+ }
+
for (unsigned j = 0; j < i; j++)
{
unsigned HOST_WIDE_INT s = min[j].m_non_jt_cases;
@@ -1200,10 +1213,15 @@ jump_table_cluster::find_jump_tables (vec<cluster *> &clusters)
if ((min[j].m_count + 1 < min[i].m_count
|| (min[j].m_count + 1 == min[i].m_count
&& s < min[i].m_non_jt_cases))
- && can_be_handled (clusters, j, i - 1))
+ && can_be_handled (clusters, j, i - 1, max_ratio,
+ comparison_count))
min[i] = min_cluster_item (min[j].m_count + 1, j, s);
+
+ simple_cluster *sc = static_cast<simple_cluster *> (clusters[j]);
+ comparison_count -= sc->get_comparison_count ();
}
+ gcc_checking_assert (comparison_count == 0);
gcc_checking_assert (min[i].m_count != INT_MAX);
}
@@ -1241,7 +1259,9 @@ jump_table_cluster::find_jump_tables (vec<cluster *> &clusters)
bool
jump_table_cluster::can_be_handled (const vec<cluster *> &clusters,
- unsigned start, unsigned end)
+ unsigned start, unsigned end,
+ unsigned HOST_WIDE_INT max_ratio,
+ unsigned HOST_WIDE_INT comparison_count)
{
/* If the switch is relatively small such that the cost of one
indirect jump on the target are higher than the cost of a
@@ -1260,10 +1280,6 @@ jump_table_cluster::can_be_handled (const vec<cluster *> &clusters,
if (start == end)
return true;
- unsigned HOST_WIDE_INT max_ratio
- = (optimize_insn_for_size_p ()
- ? param_jump_table_max_growth_ratio_for_size
- : param_jump_table_max_growth_ratio_for_speed);
unsigned HOST_WIDE_INT range = get_range (clusters[start]->get_low (),
clusters[end]->get_high ());
/* Check overflow. */
@@ -1277,18 +1293,6 @@ jump_table_cluster::can_be_handled (const vec<cluster *> &clusters,
if (lhs < range)
return false;
- /* First make quick guess as each cluster
- can add at maximum 2 to the comparison_count. */
- if (lhs > 2 * max_ratio * (end - start + 1))
- return false;
-
- unsigned HOST_WIDE_INT comparison_count = 0;
- for (unsigned i = start; i <= end; i++)
- {
- simple_cluster *sc = static_cast<simple_cluster *> (clusters[i]);
- comparison_count += sc->m_range_p ? 2 : 1;
- }
-
return lhs <= max_ratio * comparison_count;
}
diff --git a/gcc/tree-switch-conversion.h b/gcc/tree-switch-conversion.h
index d76f19b57f6..a375e52636e 100644
--- a/gcc/tree-switch-conversion.h
+++ b/gcc/tree-switch-conversion.h
@@ -180,6 +180,13 @@ public:
return tree_int_cst_equal (get_low (), get_high ());
}
+ /* Return number of comparisons needed for the case. */
+ unsigned
+ get_comparison_count ()
+ {
+ return m_range_p ? 2 : 1;
+ }
+
/* Low value of the case. */
tree m_low;
@@ -267,9 +274,12 @@ public:
static vec<cluster *> find_jump_tables (vec<cluster *> &clusters);
/* Return true when cluster starting at START and ending at END (inclusive)
- can build a jump-table. */
+ can build a jump-table. COMPARISON_COUNT is number of comparison
+ operations needed if the clusters are expanded as decision tree.
+ MAX_RATIO tells about the maximum code growth (in percent). */
static bool can_be_handled (const vec<cluster *> &clusters, unsigned start,
- unsigned end);
+ unsigned end, unsigned HOST_WIDE_INT max_ratio,
+ unsigned HOST_WIDE_INT comparison_count);
/* Return true if cluster starting at START and ending at END (inclusive)
is profitable transformation. */
--
2.33.1
